1. Field of the Invention
The invention relates to a braking unit for use on a gyroplane in order to stop the rotor as soon as the aircraft has landed.
Thus, as the rotation speed of a helicopter rotor decreases prior to its complete stoppage, the cyclic control making it possible to check the attitude of the rotor disk loses it effectiveness.
Thus, the rotor slowing down and stopping phase should be as short as possible to reduce the risk of a gust of wind tilting the rotor disk without the pilot being able to completely oppose it by a cyclic control and then the blades can strike passengers leaving the aircraft or unwise spectators moving towards it before the rotor has completely stopped. This risk is particularly high in the case of lightweight aircraft, whose rotors are relatively close to the ground. Moreover, once stopped, the rotor must remain in a braked state in order to prevent rotation under the effect of the wind.
The rotor brake of a helicopter is normally located on the transmission system mechanism driving the main rotor or the tail rotor. The control of the brake takes place by means of a handle generally located on the top or roof of the cockpit of the aircraft. The manipulation of said handle must make it possible for the pilot to rapidly stop the rotor without it being necessary to meter the braking of the latter. The pilot must be able to as rapidly as possible free the hand used for manipulating the handle, so as to maintain the rotor in a substantially horizontal plane by means of the cyclic pitch stick, during the stopping of the rotor, his second hand then being occupied by the manipulation of the collective pitch lever.
2. DESCRIPTION OF THE RELATED ART
In order to fulfil this function on lightweight helicopters use is made of an entirely mechanical braking unit by means of which friction linings anchored on a non-rotary support member are applied to a braking disk fixed to a shaft connected to the transmission system mechanism for rotating the helicopter rotors. This mechanism is such that the blocking of the rotor is maintained for as long as the control handle is not brought into its initial state. This mechanical braking unit conventionally has means making it possible to limit the braking force, so as to maintain it at a constant value, as well as restoring means constituted by a spring and by means of which the friction linings are automatically moved away from the disk when the handle is brought into its initial position.
Although such a braking unit is generally satisfactory, it suffers from the disadvantage, due to its totally mechanical nature, of not being able to amplify or increase the force applied by the pilot to the control handle, so that the application force of the friction linings to the disk is low and the stoppage of the rotor does not take place as rapidly as would be wished by the pilot.
Moreover, the use of a hydraulic control, which would make it possible to solve this problem, is considered inappropriate, bearing in mind the frequent installation of the control handle on the roof of the cockpit, where it is not recommended that hydraulic devices be installed due to the risk of oil leaks.
The present invention specifically relates to a gyroplane rotor braking unit making it possible to solve the problems disclosed hereinbefore in connection with the existing, entirely mechanical braking units and which in particular amplifies the braking force applied to the control handle, without having recourse to complex systems such as hydraulic support and without introducing pressurized hydraulics in the vicinity of the control handle.